Add a new DynamicMeter class for runtime Meter extension

This commit is based on exploratory work by Sohaib Mohamed.
The end goal is two-fold - to support addition of Meters we
build via configuration files for both the PCP platform and
for scripts ( https://github.com/htop-dev/htop/issues/526 )

Here, we focus on generic code and the PCP support.  A new
class DynamicMeter is introduced - it uses the special case
'param' field handling that previously was used only by the
CPUMeter, such that every runtime-configured Meter is given
a unique identifier.  Unlike with the CPUMeter this is used
internally only.  When reading/writing to htoprc instead of
CPU(N) - where N is an integer param (CPU number) - we use
the string name for each meter.  For example, if we have a
configuration for a DynamicMeter for some Redis metrics, we
might read and write "Dynamic(redis)".  This identifier is
subsequently matched (back) up to the configuration file so
we're able to re-create arbitrary user configurations.

The PCP platform configuration file format is fairly simple.
We expand configs from several directories, including the
users homedir alongside htoprc (below htop/meters/) and also
/etc/pcp/htop/meters.  The format will be described via a
new pcp-htop(5) man page, but its basically ini-style and
each Meter has one or more metric expressions associated, as
well as specifications for labels, color and so on via a dot
separated notation for individual metrics within the Meter.

A few initial sample configuration files are provided below
./pcp/meters that give the general idea.  The PCP "derived"
metric specification - see pmRegisterDerived(3) - is used
as the syntax for specifying metrics in PCP DynamicMeters.

1 files changed, 4 insertions, 2 deletions

diff --git a/ProcessList.h b/ProcessList.h
index 32bdfa18..da4a50da 100644
--- a/ProcessList.h
+++ b/ProcessList.h
@@ -50,6 +50,8 @@ typedef struct ProcessList_ {
    Hashtable* displayTreeSet;
    Hashtable* draftingTreeSet;
 
+   Hashtable* dynamicMeters;  /* runtime-discovered meters */
+
    struct timeval realtime;   /* time of the current sample */
    uint64_t realtimeMs;       /* current time in milliseconds */
    uint64_t monotonicMs;      /* same, but from monotonic clock */
@@ -84,12 +86,12 @@ typedef struct ProcessList_ {
    unsigned int cpuCount;
 } ProcessList;
 
-ProcessList* ProcessList_new(UsersTable* usersTable, Hashtable* pidMatchList, uid_t userId);
+ProcessList* ProcessList_new(UsersTable* usersTable, Hashtable* dynamicMeters, Hashtable* pidMatchList, uid_t userId);
 void ProcessList_delete(ProcessList* pl);
 void ProcessList_goThroughEntries(ProcessList* super, bool pauseProcessUpdate);
 
 
-ProcessList* ProcessList_init(ProcessList* this, const ObjectClass* klass, UsersTable* usersTable, Hashtable* pidMatchList, uid_t userId);
+ProcessList* ProcessList_init(ProcessList* this, const ObjectClass* klass, UsersTable* usersTable, Hashtable* dynamicMeters, Hashtable* pidMatchList, uid_t userId);
 
 void ProcessList_done(ProcessList* this);